1. Field of the Invention
The present invention relates to a method for dilating plastic or elastomeric articles using volatile swelling agents. The invention further relates to a method for encapsulating wires, electronic components, or the like with such plastic or elastomeric articles.
2. Description of the Prior Art
It is a well established practice in the electronics industry to use shrinkable plastic tubing for insulating electrical connections and components as well as for binding wires or other components together. Shrinkable plastic articles have also found use in other fields, being used, for example, to join lengths of tubing or to seal the ends thereof. In the main, there are two classes of shrinkable plastic articles which have found widespread commercial use: "heat shrink" articles, which shrink upon the application of heat, and "cold shrink" articles, which shrink upon the evaporation of a volatile swelling agent. The invention concerns itself with this latter class of articles and, more particularly, with an improved method for using such articles.
In order to apply a cold shrink article to some object, a connection between two wires, for example, the material, is first dilated by soaking in a bath of some suitable, volatile swelling agent. The swollen cold shrink material is then placed around the item to be protected and the swelling agent is allowed to vaporize, causing the material to shrink back to its original dimensions and tightly adhere to the item.
Cold shrink materials offer an attractive and economical alternative to heat shrink materials as long as the shrinkage, which is limited to from 5 to 50 percent, is sufficient to meet the needs of the application. Cold shrink materials are less costly to manufacture than heat shrink materials and, because no heat is required to accomplish the reduction in size, cold shrink materials are more suitable for use with heat sensitive or delicate components.
As they are currently used, however, cold shrink materials do present a number of distinct disadvantages. With most commercially important shrink material, organic solvents are used as swelling agents. Those solvents which have been used in the past have generally been quite flammable. The fumes from these solvents are, at best, annoying to operating personnel, and they may actually be toxic. In either case, extensive fresh air ventilation must be provided. Further, the liquid solvents themselves tend to remove oils from the hands of an operator, causing dermatological problems if gloves are not worn. The solvents will also extract plasticizer and stabilizer from the cold shrink material if it is left in the solvent too long, leaving the material brittle.
It is the object of the present invention to provide an improved method for dilating cold shrink materials which avoids the above mentioned drawbacks of the currently used method but which retains the advangates of the same.